Sorry to hear that you had such confusion! The rep should have clarified that for you.
If you have a PDA/smartphone/Blackberry, an unlimited data plan is required because these devices are always connected. However, to use these devices to tether to your laptop, you pay extra to turn them essentially into a data card.
They're seperate features because people don't always want both. Why bundle them together when everyone doesn't need the Mobile Broadband Connect. If they were combined we would not be able to remove this feature as need be. As an alleged comm engineer you should've had the gumption and common sense to educate yourself about offered products and services. As a sales rep the guy should have shown you a pamphlet of data plans and options.
you're talking in circles...this makes my head hurt....